It seems this UC3842 is used for PFC, but also for regulating the output stage. The push-pull transformer is using SG3525, but the pulse is 50%, so the output of PFC is regulating the output voltage of the smps.
The woofer is using IRF classD driver with +/-75V, and LM3886 for tweeter is working at +/-39V.

Now the PFC won't work at all. Always blown the UC3842 and the PFC mosfet. Many SMD components like SOT23 transistor and resistors are burnt.

I think there is very difficult to fix this amp without schematic or service manual

Eva

19th April 2011 04:47 PM

Are you sure that it is UC3842? Was the old IC recognizable? Recent 8-pin continuous mode PFC controller ICs are becoming more and more common (IR1150), even with a second PWM output in them (FAN480x).

If you can't find a schematic, draw your own. First the PFC, then the push pull and input rectifier, leaving "?" boxes for unrecognizable parts. Don't be lazy, the SMPS layout does not look that difficult.

fcruz

19th April 2011 05:38 PM

and what your email so I can send the schema srm450v2

hauer0361

11th June 2011 09:19 AM

email: :cop: email address removed :cop: - I want to get the scheme srm450v2 with pulsed power supply.
Thanks friend!